Lactic acid bacteria or Bifidobacteria and their cultures (e.g., culture fluids, culture supernatants, and concentrates thereof) have been reported to be effective on improvement of the lipid metabolism, such as reduction of blood-cholesterol levels and reduction of body fat or visceral fat (e.g., Patent Literatures 1 to 6). A lot of research results have been reported on the effect of improving the lipid metabolism in humans by intake of a lactic acid bacterium. However, all such researches have yielded different results, and there is no common understanding thereamong. For example, the amount of a lactic acid bacterium to be taken is often large, and effectiveness is often evaluated with insufficiency in terms of placebo controls, double-blind experiment, and calorie control, in many literatures that demonstrate the effectiveness of intake of a lactic acid bacterium on humans (e.g., Non-Patent Literature 1). In addition, there are many reports demonstrating that intake of a lactic acid bacterium does not improve the lipid metabolism in humans (e.g., Non-Patent Literatures 2 to 4). Based thereon, the effect of improving the lipid metabolism by lactic acid bacteria is speculated to be very low.
Since lactic acid bacteria are fermentation microorganisms, in general, the live bacteria are considered to be effective, and they are often used as probiotics. Meanwhile, a treated product of a lactic acid bacterium comprising, as an active ingredient, an organic-solvent extract of the lactic acid bacterium was developed for the purpose of providing a substance having a more potent effect of improving the lipid metabolism (Patent Literature 1), although the effect thereof is limited and unsatisfactory (see Example 5 below).
In recent years, lifestyle-related diseases and metabolic syndromes are increasing due to change of eating habits and lack of physical activities. The lifestyle-related diseases and metabolic syndromes are associated with lipid metabolism abnormalities or sugar metabolism abnormalities, which often lead to the development of symptoms or diseases such as arteriosclerosis, fatty liver, hyperlipidemia, obesity, hypertension, or diabetes. When the lipid metabolism or sugar metabolism is abnormal, also, levels of lipid metabolism markers, such as cholesterol, neutral fat, and visceral fat, are known to become elevated. As such, effective means for improving the lipid metabolism are still needed in order to prevent or treat such lifestyle-related diseases and metabolic syndromes.